This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Surface enhanced Raman spectroscopy (SERS) nanoparticles have distinct spectral bands that can be exploited for biomedical diagnostics. In particular, SERS particles have emerged as promising beacons for flow cytometry. Because SERS particles have distinct Raman spectra with high signal to noise, they have the potential to be used for multiplexing assays that require not only great dynamic range but also narrow spectral bandwidths to discriminate between events . We are working towards the characterization of SERS particles using flow cytometry systems developed at LANL, including the spectral, phase-sensitive and high-resolution instruments.